Remote self-synchronous control system



Feb. 28, 1950 A. G. cooLEY REMOTE sELF-sYNcHRoNoUs CONTROL SYSTEM FiledDec. 17, 1947 5 sheets-sheet 1 IN VEN TOR. @05W/V 5 Comfy 'y j?,QTTP/Vf/ Feb. 28, 1950 A. G. cooLl-:Y

I REMOTE SELF-SYNCHRONOUS CONTROL SYSTEM Filed Deo. 17, 1947 3Sheets-Sheet 2 Feb. 28, 1950 A. G. cooLY REMOTE SELF' -SYNCHRONOUSCONTROL SYSTEM l3 Sheets-Sheet 5 Filed Dec. 17, 1947 JNVENTOR. Alvar/m GCOOLfy Patented Feb. 28, 1956 REMOTE SELF- SYNCHRONOUS CONTROL .SYS TEMAustin G. Cooley, New York, N. Y., assgnor t Times FacsimileCorporation, New- York, N. Y.,

a corporation of New York Application December 17, 1947, Serial No.'792, 313

(Cl. S18- 24) 8 Claims. 1

This invention relates to remote control systems and more particularlyit relatesv to servomotor arrangements for use in such systems.

A principal object of the invention is to provide a remote controlsystem of the type employing a source of single phase control signalswhose phase is varied for the remote positioning of a distant shaft. Thedistant shaft is driven by a main alternatingv current motor haying arotor and stator at least one of which is adapted to be energized by apolyphase alternating current, in conjunction with a. compensating ortorque balancing motor connected to the irst motor for preventing thefirst motor from tending to creep or continuously rotate in synchronismwith the polyphase alternating current. As a result, the main motorturns only when the phase of thesaid control signals is changed and'toan extent determined by the amount of such phase change.

Another object of the invention is to provide an improved servo-motorsystem, wherein the servo-motor has its stator continuously excited froma polyphase alternating current supply source and its rotor excitedunder controlA yof a signal-controlledk single phase source, or viceversa, that isY with the rotor excited Yby a polyphase alternatingcurrent andthe stator excited from a single phase source.

Another object of the invention is to provide an improved arrangementfor controlling a servomotor from a remote signal-controlled singlephase alternating current source, theservo-motor being energized from apolyphase alternating current source; together with means for preventingtendency of the rotor torotate when the phase-of the control signalremains unchanged.

Another object is to provide a main servomotor which is excited locallyby polyphase al.- ternating cur-rent the rotory Aorstator excitationbeing controlled by a remote single phase alternating current` source;in conjunction .with another or auxiliary servo-motor which inhibitsrotation of the rotor of the main servo-motor when the single phasesignal is not being changedV in phase, or if the rotor of the; mainmotor is opencircuited.

' A feature of the invention relates lto Aa rnain servo-motor which isarranged to have its. stator excited from a three-phase alternatingcurrent source, and its rotor excited from a single phase source theinstantaneous phase o i which ,can `be varied in accordance withsignals; in conjunction with a similar auxiliary servo-.motor v.wl'lichalso hasy its stator excited irom said three-phasesource but with itsrotor connected to an artificial line or electric network whichsimulates the impedance of the signal-controlled phase shifting deviceassociated with the main motor. L

Another feature relates to a remote control system having a pairofalternating current motors each` with a three-phase stator and asingle phase rotor. One of the single phase rotors is arranged to beexcited by an adjustable Single phase alternatingv current; and thestators are connected for excitation from the saine three-phasealternating current supply source. The rotors of the two motors aremechanically connected to a common shaft to be controlled while thestators are excited` from the, same three-phase source in such a Waythat one motor tends to oppose rotation of the other motor While thephase of said single phase current remains constant.

A further .feature relates to a servo-motor systeni employing, apolyphase servo-generator and a polyphase servo-motor 4controlledthereby, together with means for preventing rotation Yof the rotor ofthe servo-motor except when variable phaseA signals are received from aremote control point. v 4

A still further feature relates. to the novel organization, arrangementand v .relative interconnection ofv parts which cooperate to provide anVimproved remote controlv system of the servomotor type.

Fig. 1 of the drawing shows in composite block diagram form andschematic vwiring form, a typi-y cal remote -control system embodyingfeatures ofy the invention.r

Fig. 2 is a modification of Fig. 1.

Fig. 3 is another modication of Fig. 1.

The. ordinary servo-motor system employing@ synchro-generatory and asynchro-motor are connected so that the` rotors of both motors areexcited by a single phase alternating current, and the stators areVeither delta or Y connected' to provide a three-phase interconnectingcircuit between the generator. and motor. The rotor of .thesynchro-generator is arranged to be turned through any desired anglerepresent/,ing a signal, and the rotor of the synchro-motor electricallyfollows the rotation of thegenerator rotor. In other types offolloyv-upv systems, for .example in the so-called Selsyn the stator ,ofthe synchrq. generator is supplied from a two-phase alternating currentsource, however, the two-phase power is split into three, windings of atypical threephase arrangement, either delta or Y. Withsuch anarrangement, if one of` the stator windings receives power at zerophasathe other two windj- 3 ings receive power 180 displaced from thefirst winding but the power in the second or third Winding is less thanthat of the first winding, while the resultant power in the second andthird winding is equal to that of the rst winding. If with such aconventional construction of servo-generator or servo-motor, attemptsare made to excite the stator with balanced threephase current, therotor will start turning as if it were the rotor of an induction motorof the squirrel-cage type.

of synchro-generators or synchro-motors from a three-phase alternatingcurrent source. It is necessary in certain types of remote controlsignalling systems to provide a servo-motor which has no tendency torotate in either direction unless a phase shifted signal is applied tothe rotor; and yet it is necessary to provide accurate rotationalcontrol of the rotor in response to the phase variations of the appliedsignal. A typical arrangement, according to the invention, foraccomplishing these results is shown in the drawing.

Referring to the drawing, the block I represents any suitable source of60-cycle single phase alternating current supply, whose frequency andphase are held within rather close limits. Source I is connected to thestationary element 2 of any well-known form of electrical phase shifternetwork whose adjustable element 3 is mechanically connected to anadjusting wheel or handle 4 associated with a phase or angle rcalibratedscale 5. The output of the phase changer 6 is therefore a single phase60-cycle alternating current signal whose phase can be adjusted by meansof the member 4. It will be understood of course that the member 4,instead of being operated locally, can be operated remotely in responseto signals representing any selected phase or angular position of member4.

The output of device 6 is applied over the conductors 1, 8, to thesingle phase winding 9 of a rotor I0. Associated with rotor Ill is astator II, having its windings connected for three- -phase excitation,either delta or Y, from the three-phase 60-cycle power source I2.Preferably, source I2 is connected to source I Via'a transmission lineand provided with well-known arrangements for maintaining thefrequency'of sources I and I2 constant. 4Rotor I0 and stator II can beof any well-known construction such as customarily employed insynchro-generator or synchro-motor devices. lFor a detailed descriptionof such synchros, reference may be had to chapter XII, article l, pages12-3 and 12-4 of Principles of Radar, published by McGraw Hill BookCompany, Inc., New York, New York.

The shaft I3 carrying rotor I6 is connected to a pointer I4, which isassociated with a phase or angle calibrated scale I5. With such anarrangement, if the circuit to winding 9 is open or if the phase remainsconstant, there is a tendency for the rotor III to rotate as if it werethe rotor of an induction motor of the squirrel-cage type. In order toovercome this tendency to rotate, the shaft I3 is connected to the rotorI of a similar synchro-motor whose rotor winding II is connected byconductors I8, I9, to an electrical load in the form of an artificialline 20, comprising for example the resistance 2I and the reactance 22.Ther reactance 22 may take the form of an inductance, a capacitance, ora combination of resistance, inductance and capacltance, as iswell-known inthe artificial line For this reason, it has noti beenpracticable heretofore to excite the stators 4 art. This artificial linehas its elements so proportioned as to have the same impedance Aas theimpedance facing the winding I6 from the device 6. The stator winding 23of this auxiliary servo-motor is likewise the same as the winding II ofthe main servo-motor, and it is connected in a three-phase arrangementto the source I2. However, two of the leads from the source I2 arereversed as compared with their connection to stator II so as to insurethat the torque of rotor I6 is opposed to that of rotor I0. Thus, if thecircuits to both rotors I0 and I6 are open, and if the stators of bothmotors are energized from the source I2, the system vis well-balancedand there is no tendency to spin or take off so that the shaft I3remains stationary. However, if the rotor winding 9 is supplied withsingle phase power through the device 6, and if the rotor winding I'Iwere disconnected from the device 20, the rotor IIJ would then tend tocontinuously rotate by squirrel-cage induction motor action even thoughthe member 4 is held stationary. On the other hand, when the winding Ilis connected in circuit with the artificial line 26 and the winding 9 isconnected to the device 6, the above-mentioned torque tending to rotateshaft I3 by means of rotor I0, is counter-balanced by an equal andopposite torque from rotor I6. Consequently, if the member 4' is rotatedto represent a phase angle signal, the pointer I4 will respond Veryaccurately to variations in position of the said member 4. While thedrawing shows a frictional or mechanical damper 24 which couples the tworotors I0 and I6 together, it has been found that this mechanical damperis not entirely necessary, its function being primarily to act as acushion between the two sections of the shaft I3 while enabling rotarytorque to be positively transmitted from one section of the shaft to theother. In that case the rotors Il] and I6 can be mounted on the sameshaft which carries the pointer I4. Preferably, the elements 2I and 22of the artificial line 20 are adjustable so as to match the impedance ofthe line I'I--I8 to the input impedance of the winding 9. For a detaileddescription of the manner of matching the said impedances, reference maybe had to Radio Engineers Handbook by F. E. Terman, first edition,published by McGraw Hill Book Company, Inc., New York and London, 1943,pages 20S-268 and 210-215.

While in the foregoing description, the motors are shown with a singlephase rotor and a polyphase stator, these motors may be of a type havinga polyphase stator and a single phase rotor; Thus, as shown in Fig. 2,wherein the parts which are identical with those of Fig. l bear the samedesignation numerals, the singlephase 60- cycle signal which is sentover line 'I, 8, is connected to the single phase stator winding 25,while the three-phase current from the device 26 is supplied to thethree-phase windings on the rotor 2l. Likewise, this three-phase currentis applied to the three-phase windings of the rotor 28 of thecompensating motor, and the single phase stator Winding 29 of thiscompensating motor is connected to the articial line 20 for purposesabove described. In Fig. 2, the device 26 instead of being a separatethree-phase 60- cycle source which is maintained at the same frequencyas the source I, may consist of any well-known phase splitter forreceiving the single phase 60-cycle current from source I over thetransmission line 30 and convertingV it into anni,

a three-phase signal of; thesameO-Cycle frequency.

While in the foregoing the motors have'been describedV as having athree-phase stator winding (Fig. 1) or a three-phase rotor winding (Fig.2), it will be understood that the stators of Fig. 1 and the rotors ofFig. 2 can be other polyphase windings, for example two-phase windings,supplied with the appropriate polyphase alternating current, for exampleby a two-phase GO-cycle current. It is understood that in all cases thevarious phases of the polyphase current are supplied to the polyphasewindings of the auxiliary motor so as to produce under the conditionshereinbefore described, a torque which is opposite to that produced inthe main motor which is controlled over line 18.

If desired, the auxiliary or compensating motor can have a polyphaserotor 3| and a polyphase stator 32 with the stator windings connected tothe polyphase source l2 or 26 and with its polyphase rotor connected toan articial line. Such an arrangement is shown in Fig. 3, wherein theparts which are identical with those of Figs. 1 and 2, bear the samedesignation numerals. In this embodiment, the main motor has athreephase rotor 33 and a three-phase stator 34. The adjustable phasesingle phase signals from the device 6 transmitted over the lines 1 -8,are applied to a 1-to-3-phase splitter 35, for dividing the single phasecontrol signals into corresponding balanced three-phase control signalswhich are applied to the stator 34 of the main servomotor. Likewise, thesingle phase Gil-cycle signals from the source I are applied to a1-to-3- phase splitter 26 and thence to the rotor 33 of the main motor.The auxiliary or compensating motor has a three-phase rotor 36 which iscoupled to the shaft I3 and this rotor has its windings connected to abalanced three-phase artificial line 31 which is proportioned so as toreflect an impedance into the windings of rotor 36 which impedance isequal to the input impedance of the windings of stator 34.

Various changes and modifications may be made in disclosed embodimentswithout departing from the spirit and scope of the invention.

What is claimed is:

1. Apparatus of the type described, comprising a master shaft, a slaveshaft, an alternating current motor which is to be remotely controlledfrom said master shaft to position said slave shaft, said motor having asingle phase rotor and a three-phase stator, a similar auxiliary motorhaving a single phase rotor and a threephase stator, means connectingthe stator windings of both motors to the same source of threephasealternating current supply, means connecting the rotor winding of therst motor to a source of adjustable single phase alternating current,and means connecting the rotor of the auxiliary motor to an electricalload network whose impedance is matched with the input impedance to therotor of the rst-mentioned motor.

2. Apparatus according to claim 1 in which the phase excitation of thestator of said auxiliary motor is related to the phase excitation of thestator of the first motor to apply equal and opposite torque to saidslave shaft when the phase of the single phase alternating currentremains unchanged.

3. Apparatus according to claim 1 in which the rotor of themst-mentioned motor is coupled to therotory ofl the auxiliary motorthrough a; mechanical damping device.

1. Apparatus of the. type described, comprising a source of alternatingcurrent signals of adjustable phase, a remotely located servo-motorwhose. rotor is. connected to said source. and

whose stator is connected to av source of poly-v phase alternatingcurrent so that normally said motor tendsto rotate even whenv the phaseof said alternating current signals remains cone Stan-t, a. stabilizingmotor having its. rotor coupled to the rotor of said servo-motor andexcited from said polyphase source to oppose the said tendency to saidservo-motor to rotate except when the phase of the signals from saidsource is being adjusted.

5. Apparatus according to claim 4 in which the said stabilizing motorcomprises a polyphase stator which is excited from said polyphasesource, and a single phase stator which is connected to an electricalload whose impedance matches the input impedance to the ro-tor of saidservo-motor.

6. Apparatus of the type described, comprising a source of single-phasealternating current, a signal-controlled phase shifter having its inputsupplied from said source, means to derive a polyphase alternatingcurrent from said source, a main alternating current motor to beremotely controlled, said motor having a single phase stator winding anda polyphase rotor winding, means connecting said rotor winding forcontinuous excitation with polyphase alternating current, meansconnecting said stator winding with the output of said phase adjuster,and an auxiliary alternating current motor having its rotor mechanicallycoupled to the rotor of the first motor, the stator of the auxiliarymotor being connected for excitation by said polyphase source, and therotor of said auxiliary motor having a winding connected to anadjustable electrical load network.

7. Apparatus according to claim 6 in which said auxiliary motor has apolyphase rotor which is supplied with said polyphase alternatingcurrent, said auxiliary motor having a single phase stator which isconnected to an artificial line for the purpose described, theconnection of the phases of said auxiliary motor being such as to causesaid auxiliary motor to have an opposite torque to that of said mainmotor when the phase of the single phase current applied to the statorof the main motor remains unchanged.

8. Apparatus of the type described, comprising a source of single-phasealternating current, a signal-controlled phase shifter having its inputsupplied from said source, a source of polyphase alternating currentsynchronized in frequency with the vfrequency of said single-phasesource, a main alternating current motor having stator and rotorwindings one of said windings being a single-phase winding and the otherbeing a polyphase winding, means connecting the output of said phaseshifter to the single-phase winding of said motor, means connecting thepolyphase winding of said motor to said polyphase source, an auxiliaryalternating-current motor having a stator winding and a rotor windingone of said windings of the auxiliary motor being a single-phase windingand the other being a polyphase winding, means mechanicallyinterconnecting the rotors of both motors together, means connecting thepolyphase winding of the auxiliary motor to said polyphase source, andmeans connecting the single-phase winding of the aux- 8i iiafy otr to`an adjustable impedance-match- FOREIGN PATE-NTS, ing electricalnetwork-.for the purpose described. 1 i Y AUSTIN G, C0QLEY- NumberCountry Date y 487,457 Great Britain June 14, 1938 REFERENCES CITED vOTHER REFERENCES yThe following references are of record in the GeneralElectric Review v01 39 No 6 Jfu fille of this ygiatterrt:`

` 1936, pp. 274-279. Y UNITED STATES PATENTS Number Name Date l 10633,690 Franke Sept. 26, 1899

